The present invention relates to a ribbon cartridge for a typewriter or similar office machine of the type which is constructed to achieve sound damping.
Among numerous known provisions for damping noises that are perceptible in the vicinity of typewriters and similar printing machines, especially teleprinters and memory typewriters, devices for shielding persons located in the vicinity of the machine from impact noise caused by the type characters striking the paper are becoming particularly important. Sound-absorbing hoods which either encompass the entire machine or are placed above the platen in the area where the paper is introduced have proved to be particularly effective. In the case of sound hoods which encompass the entire machine, it is still possible to observe the typewritten text through a view window; however, access for the purpose of inserting and aligning the paper and making corrections is extremely inconvenient. For this reason, sound hoods of this type are not suitable for offices where it is frequently necessary to insert new sheets of paper.
Those types of covers which are placed only over the means for introducing and removing paper in the vicinity of the platen permit the operator of the machine to reach the paper much more easily. In this case, however, the result is often that the desired degree of noise damping cannot be achieved. While the operator is generally able to observe the printed text satisfactorily with this kind of sound-absorbing hood, a particular problem is the accessibility of the printing mechanism when the type wheel and ribbon cartridge must be changed. Furthermore, the sound-absorbing hoods which cover the platen are too expensive for lower-cost typewriters intended, for example, for typing personal correspondence in the home.
Furthermore, if a machine, especially an electric typewriter, is surrounded by a housing, then a noise buildup occurs in the interior of the housing, thus increasing the noise intensity. The sound waves striking the housing from the inside or striking flat-surfaced structural parts cause parts which are capable of vibrating to vibrate, which in turn is a source of machine noise transmitted to the outside.
In order to reduce this noise buildup, a ribbon cartridge has become known whose bottom and top cover plate are provided with holes. It is true that these holes do reduce the sound buildup and reduce the intensity of noise in the interior of the housing. However, material, such as carbon particles, worn away from the used carbon ribbon because of the guidance and drive of the ribbon falls through the holes in the base plate and soils parts of the machine located below it. This soiling sooner or later causes problems with the functioning of the machine.